The present invention relates to the protection of surfaces exposed to reactants in substrate processing systems. More specifically, the present invention relates to a substrate processing apparatus having a carbon-based coating, such as diamond or diamond-like carbon (DLC), on surfaces exposed to reactants and a method for applying and maintaining such coatings.
The processing of substrates requires a carefully controlled environment to avoid contamination from ambient chemical species and defects caused by particulates. Therefore, substrate processing steps take place in the controlled environment of a processing chamber. These steps include operations such as deposition, etching, sputtering and diffusion. In the production of a finished substrate, each of these operations serves a function such as applying, patterning and manipulating the characteristics of the various layers required by the given technology during the course of manufacturing semiconductor devices and circuits.
Some of the gases used during substrate processing are especially corrosive, and tend to etch material from the processing chamber's interior surfaces. Thus, one of the difficulties confronting users of substrate processing systems is the etching experienced by components exposed to reactants. Attack of these components is particularly severe during etching and cleaning procedures. For example, as a film is deposited on a substrate, some of the material being deposited also accumulates on the processing chamber's walls and must be removed periodically. This removal is done during cleaning operations in which process gases are evacuated from the processing chamber and an etchant gas such as CF.sub.4 or NF.sub.3 is introduced. A plasma is then formed from the etchant gas in order to etch away residues accumulated on the processing chamber's interior. Such cleanings may be required as frequently as every one to three substrates.
Unfortunately, etching of the processing chamber's components often occurs during such cleaning. A fundamental reason for the over-etching experienced by certain interior surfaces is the varying thickness of the accumulated residues. Some of the chamber's interior surfaces accumulate more residue due to their location, their constituent materials and other factors. The cleaning step, however, generally continues until substantially all residues are removed from the processing chamber's interior surfaces. Thus, some surfaces will become residue-free before others. Over-etching occurs when these residue-free surfaces (and those which do not experience residue accumulation) are exposed to constituents from the etchant plasma.
Poor resistance to the cleaning process and other corrosive operations (such as etching) is a limiting factor in terms of machine reliability (i.e., shortened component lifetime). Over-etching of the interior surface of the processing chamber or other components reduces the useful lifetime of such components, decreases substrate throughput as the worn out components are replaced, increases the cost of consumables, and may lead to particle contamination. Furthermore, this lack of etch resistance limits methods of enhancing machine productivity, such as increasing the cleaning rate (e.g., by the use of higher RF power in the cleaning operation).
Accordingly, it is desirable and important to extend the lifetime of processing chamber components that come into contact with the reactants used in substrate processing systems. Resistance to the etchants employed in substrate processing systems is thus desirable. The accumulation of residues should also be reduced to the extent feasible, as should the release of particulates. Finally, the release of impurities from the processing chamber's components should be minimized.